import java.util.Scanner;

/**
 * Created by dllo on 18/3/30.
 */
public class Qestion01 {
    public static void main(String[] args) {
        Scanner scanner= new Scanner(System.in);
        System.out.println("用户输入的一个数");
        int num=scanner.nextInt();
        int sum = 0;
        for(int i = 1;i <=num ;i++){
            sum = sum +i;
        }
        System.out.println(sum);


    }

}
